Abstract: An aerial spray boom 11 for an aircraft includes: an elongated housing 21 secured to the aircraft wing 12, the housing having one or more openings 22 along its length; a conduit 23 having a liquid supply passage 26 and a plurality of spaced-apart nozzles 27 that are aligned with, or extend through housing openings 22, conduit 23 being mounted in said housing for arcuate movement about its longitudinal axis through a prescribed arc that defines variable spraying positions; and a conduit actuator 31 operative connected to the conduit 23 that moves the conduit relative to the housing through an arc.